Hyperbolic metamaterials (HMMs) are artificially-structured materials engineered to create hyperbolic dispersion for optical waves. They have attracted attention because of the supported propagating high-k modes and the enhanced photonic density of states. While metal is the most common conducting constituent element in HMMs, graphene provides another useful building block, i.e., a truly two-dimensional (2D) conducting sheet whose conductivity can be controlled by doping. In this presentation, I will first introduce an ellipsometry technique we developed specifically for characterizing optical properties of 2D materials. Following that, I will present our recent experimental realization of a multilayer structure of alternating graphene and aluminum oxide layers, a structure similar to the metal-dielectric multilayers commonly used in creating visible-wavelength HMMs. Our characterization with an infrared ellipsometer demonstrates that the metamaterial experiences a optical topological transition from elliptic to hyperbolic dispersion at mid-infrared frequencies.